Is the severity of a pathogenic illness dependent on the number of pathogens?

How many pathogens are needed to cause a full-blown infection? A single disease pathogen, for example, is virtually harmless. But is there a critical value of the number of disease pathogens that are needed to cause an illness? And once that critical value is reached, is the severity of the illness related to the concentration of pathogens in key regions? Does the concentration of pathogens usually vary from illness to illness? (depending on onset of immune system response and on "resources" that the virus can exploit?) Are there any resources I could consult regarding the pathogenic concentration of an illness plotted as a function of time?

How many pathogens are needed to cause a full-blown infection? A single disease pathogen, for example, is virtually harmless. But is there a critical value of the number of disease pathogens that are needed to cause an illness? And once that critical value is reached, is the severity of the illness related to the concentration of pathogens in key regions? Does the concentration of pathogens usually vary from illness to illness? (depending on onset of immune system response and on "resources" that the virus can exploit?) Are there any resources I could consult regarding the pathogenic concentration of an illness plotted as a function of time?

I varies from pathogen to pathogen, the severity of the symptoms might dependent on the dose depending on the infection load and in some cases one bacteria or one virus sufficient to cause a "full-blow" infection.

Interesting. It's as if whenever there is an unexploited niche, it's always going to be exploited (kind of like what evolutionary theory would predict with respect to unexploited ecosystems, or how economics would predict with respect to unexploited opportunities).